Electron microscope specimen



Patented Mar. 11, 1947 ELECTRON MICROSCOPE SPECIMEN V "James Hillier, Cranbury, N. J., assignor-to Radio Corporation of America, a corporation of Delaware ' Application December 24, 1943, Serial No. 515,581

13 Claims. (01. 250-495) This invention relates generally to electron microscope technique and more particularly to improved methods of and means for providing relief copies of microscopic specimens for use in electron microscope investigations.

Frequently, microscopic specimens of materials are too thick ortoo dense to permit satisfactory electron microscopic investigations by means of electron transmission through the specimen. Various methods have been employed for providing relief copies of such specimens by molding electron permeable elements in direct contact with the original specimen, andthence placing the molded copy of the specimen in the object chamber of the electron microscope. Such copies are not entirely satisfactory for transmission electron microscopy, since the copies are not characteristic of the internal structure of the specimen. Furthermore, minute air bubbles between the specimen and the copy or imperfect register therebetween sometimes provide an extremely poor copy of the original specimen.

The instant invention contemplates improved methods of and means for juxtaposing a very thin electron pervious element substantially in contact with the microscopic specimen. The electron pervious element may, for example, comprise an extremely thin layer of a metallic bi.- chromated gel, which is supported by an extremely thin membrane of collodion or other electron pervious material. The specimen andthe juxtaposed element are irradiated from a' point source of short wavelength radiation such as, for

example, soft X-rays or high velocity electrons,

whereby the metallic bichromated gel is irradiated by X-rays or electrons transmitted by the relatively thick specimen. Tanning of the bichromated gel 'will' besubstantially proportionalto .the intensity of the radiation transmitted by the specimen. The untanned or partially tanned portionsof the bichromated gel may be removed by dissolving these portions in, for example, warm water. The residual tanned material therefore will vary in thickness and density as a-function of the thickness and density of the original specimen. The relief copy of the specimen thus pro,- vided may be made as thin as desired; thereby providing a satisfactory specimen copy forJele'c tron microscope investigation in the usual manper. .4 'g" to provide an improved method of and means for exposing an electron pervious element to X-ray irradiation -by transmission through a relatively e c i pervious specimen for providing a relief copy of said impervious specimen for electron microscopic observation.

A furtherobject of the invention is to provid an improved method of and means for providing accurate relief copies of relatively dense microspecimens by irradiating an electron pervious element by highvelocity electrons transmitted (through said dense specimen to provide a microscopic specimen copy characteristic of the electron transmission characteristics of the original specimen; An additional object of the invention is to provide an improved method of and means .for subjectingan electron pervious material to radiations of *short wavelength by transmission through a relatively dense microspecimen, and by removing portions of said irradiated element as a function of the transmitted radiation image of the original specimen. 7

The" invention will be further described by reference to the accompanying drawing of which Figure 1 is a partially schematic elevational view .of the technique involved, Figure 2 is a fragmentary cross-sectional view of one embodiment of the'flnal product obtained in accordance with the invention and Figure 3 is a fragmentary cross- .sectional-view of a secondembodiment of the final product obtainedin accordance with the invention. Similar reference-characters are applied to similar elements throughout the drawing. 1

Referring to Figure 1,,a microscopic specimen I ,is secured to-an extremely thin supporting membrane 3 such, for example, as a; thin collodion membrane 4 formed by dropping diluted collodion on a water surface. The collodion-membrane 8 is supported by a metallic ring 5. This method The electron permeable element H comprisesa thin layer of material which is sensitive to radiations of short wavelength such as, for example, soft X-rays or high velocity electrons. JSuch materials" include metallic bichrom'ates which may be combined with gelatin or gum arabic. For example, a satisfactory radiation sensitive element for use with soft X-rays :may :be obtained by employing a potassium bichromated gel supported by a thin membrane oi collodion.

The radiation sensitive element l,'*juxtaposed substantially in contact withthe specimen l, is

subjected to soft X-rays or' relativelyfhigh velpcterials not specifically disclosed herein may be substituted for the specific materials described without departing from the spirit and scope of the methods and products disclosed. For example, egg albumen may be substituted for the gelatin or gum arabic. The type of irradiating source also may be selected to provide the proper transmission contrast for the particular microscopic specimen which is to be copied and the particular radiation sensitive substance may be selected accordingly to provide the desired sensitivity and contrast. I v

Thus the invention disclosed comprises improved-methodso'f and'means 'for securing accurate relief copies of specimens by irradiation and chemical decomposition of radiation sensitive elements subjected to short wavelength radiations transmitted by said specimens.

I claim as m iinvention:

1. The method of deriving from a radiation g-pervious element, having at least a radiation ity electrons derived from a remotely situated point source of such radiations I3. characteristic of the permeability of the specimen to the radiation source is obtained upon the radiation sensitive element by transmission of the radiations through the specimen to the "radiation sensitive element H. -The transmitted X-ray's or high velocity electrons change the chemical composition, or ten, the radiation sensitive element II "as "a function o'fthe radiation transmission characteristics of "the specimen I. It should be understood that many specimens which offer poor transmission "for electrons are relatively pervio'us to 'X-rays. "Hence, X-rays maybe employed "for -exposin'g't'he radiation sensitive element 11 in instances where electron transmission by the specimen I would 'involveex tremely long exposure intervals, or would necessitate extremely high velocity irradiating electrons. Any conventional means may "be employed for providing the point source of 'X-ray 'or high velocity electron radiation.

After irradiation of the radiation sensitive element H for a time interval sufficient to prov'ide a suitable relie'f image of the specimen, the

radiation sensitive element ll, supporting mem- Lbrane 9 and supporting rin 1 maybe immersed in a solution for dissolving or removing theuntanned or partially tanned 'portionsof the exposed sensitive element. For example, if the radiation sensitive element comprisesa metallic bi- "chromated gelatin, the partially tanned and untanned portions-thereof' may be removed by 'immersing the element in warm-water. If the-metallic bihromate is combinedwith, for example, gum arabic. the untanned or partially tanned portions may be removed by immers'ingthe element. in cold water.

The completed relief copy of the microscopic specimen I is shown in the cross-sectional fragmentary views of Figures? and "3 wherein the section of a tannedmetallio bichromate gel which an image sensitive portion, an electron permeable relief copy of a microscopic specimen comprising juxtaposing said radiation pervious element in close relation with said specimen, irradiating at least said radiation sensitive portion by transmission through said specimen to provide a relief image :on said sensitive surface, and modifying the electron permeability of portions of said irradiated element in relation to said image'irradiation :thereof.

-2. The method of deriving vifrom'a radiation 'pervious element, having at least-aradiation sensitive portion, an electron permeable relief copy of 'a microscopic specimen which is too thick for satisfactory continuous electron transmission miof a microscopic specimen whichi's too thick for satisfactory continuous electron transmission microscopy comprising juxtaposing substantially in contact with said specimensaid radiation sensitive portion of said radiation'pervious element,

irradiating said specimen by relatively short -wavelength radiations, irradiating .at least said radiation sensitive portion by transmission upper surface is characteristic of the relief con- 7 ltourof the specimen I after immersion in thesolution which dissolvesthe untanned or partially tanned portions. Figure 2 illustrates a crossis self supported on the supporting ring 1. 'Fi

urelB illustrates: a similar completed relief copy ofgthe' specimen I wherein the tanned metallic bichroiriate gel isfsfupported by a collodlon 'mem- 1 Itshoiildbe understood-that variousotherma' "lorane "ii-which, in turn,'is supported by the sup' p rtinence-* through said specimen to provide a relief image on said sensitive surface which is suitable for substantially continuous transmission microthick for satisfactory continuous electron transmission microscopy comprising juxtaposing substantially in contact with said specimen'said :ra-

di'ation sensitive'portion of said radiation-pervious element, irradiating said specimen by X-ray radiations, irradiating at least said radiation sen- 25 sitit-e' portion b 'xay transmissibn'trirou'gh said specimen. to, provide arelief'i'ma'geon said sensitive surface which is suitable for substantially continuous transmission, microscopy, and removing portions of saidirradiated"element in inverse relation to said'flmage irradiation thereof.

5. The method of deriving: from an electron pervious element, having at least an X-ray radiation sensitive portion, an"el'ectron'permeable relief copy' of a microscopicspeimen which is too. thick for satisfactorycontinuous electron transmission microscopy comprising juxtaposing substantially in contact with said specimen said X-ray radiation sensitive portion of said electron pervious element, irradiating said specimen by relativel short wavelength X-ray radiations, irradiating at least said radiation sensitive portion by X-ray transmission through said specimen to provide a relief image on said sensitive surface which is suitable for substantially continuous electron transmission microscopy, and removing portions of said irradiated element in inverse relation to said X-ray image irradiation thereof.

6. The method of deriving from an electron pervious element, having at least an X-ray radia-- tion sensitive portion, an electron permeable relief copy of a microscopic specimen which is too thick for satisfactory continuous electron transmission microscopy comprising juxtaposing substantially in contact with said specimen said X-rav radiation sensitive portion of said electron pervious element, irradiating said specimen by rel tively short wavelength X-ray radiations, irradiating at least said radiation sensitive portion by X-ray transmission through said specimen to provide a relief image on said sensitive surface which is suitable for substantially continuous electron transmission microscopy, and chemically dissolving and removing portions of said irradiated elements in inverse relation to said X-ray image irradiation thereof.

'7. The method of deriving from an electron pervious element, having at least an electron sensitive surface portion, an electron permeable relief copy of a microscopic specimen which is too th ck for satisfactory continuous electron transmission microscopy comprising juxtaposing substantially in contact with said specimen said electron sensitive portion of said electron pervious e ement, electron irradiating said specimen, electron irradiating at least said electron sensitive surface portion by electron transmission through said specimen to provide a relief image on said sensitive surface which is suitable for substantially continuous electron transmission microscopy, and removing portions of said irradiated element in inverse relation to said electron image irradiation thereof.

8. The method of deriving from an electron pervious element, having at least an electron sensitive surface portion, an electron permeable relief copy of a microscopic specimen which 'is too thick for satisfactory continuous electron transmission microscopy comprisin juxtaposing substantially in contact with said specimen said electron sensitive portion of said electron pervious element, irradiating said specimen, electron irradiating at least said sensitive surface portion by electron transmission through said specimen to provide a relief image on said sensitive surface which is suitable for substantially continuous electron transmission microscopy, and chemically dissolving and removing portions of said irradiated element in inverse relation to said electron image irradiation thereof.

'9. Ah eiectronipermeablereliercopyaria: micro scopic specimen said copy comprising'a radiation sensitive electron'pervious :element which .is produced by juxtapositionwith said-specimen, by irradiation by transmission through "said specimen to provide a radiation relief image, and whereinthe electron permeability of portions or said element are modified in relation to said image irradiation thereof.

10. An electron permeable relief "copy-1 of- 'a microscopic specimen said copy comprising a radiation sensitive electron pervious element which is produced by juxtaposition with said specimen, by irradiation by transmission through said specimen to provide a radiation relief image,

and wherein portions of said element are chemically removed in inverse relation to said image irradiation thereof.

11. An electron permeable relief copy of a microscopic specimen said copy comprising a radiation sensitive electron pervious element which is produced by juxtaposition with said specimen, by irradiation by transmission through said specimen to provide a radiation relief image, and wherein portions of said element are chemically dissolved and removed in inverse relation to said image irradiation thereof.

12. An electron permeable relief copy of a microscopic specimen said copy comprising a radiation sensitive electron pervious element including bichromated colloids which is produced by juxtaposition with said specimen, by irradiation by transmission through said specimen to provide a radiation relief image, and wherein portions of said element are chemically removed in inverse relation to said image irradiation thereof.

13. An electron permeable relief copy of a microscopic specimen said copy comprising a radiation sensitive electron pervious element including a metallic bichromate gel which is produced by juxtaposition with said specimen by irradiation by transmission through said specimen to provide a radiation relief image, and

wherein portions of said element are chemically removed in inverse relation to said image irradiation thereof.

14. An electron permeable relief copy of a microscopic specimen said copy comprising a radiation sensitive electron pervious element including a metallic bichromate and gum arabic which is produced by juxtaposition with said specimen, by irradiation by transmission through said specimen to provide a radiation relief image, and wherein portions of said element are chemically removed in inverse relation to said image irradiation thereof.

15. An electron permeable relief copy of a microscopic specimen said copy comprising a radiation sensitive electron pervious element including metallic bichromated egg albumen which is produced by juxtaposition with said specimen, by irradiation by transmission through said specimen to provide a radiation relief image, and wherein portions of said element are chemically removed in inverse relation to said image irradiation thereof.

16. An electron permeable relief copy of a microscopic specimen said copy comprising a radiation sensitive electron pervious element including potassium bichromate and gelatin which is produced by juxtaposition with said specimen,

by irradiation by transmission through said specimen to provide a radiation relief image, and

wherein portions of said element are chemically gamma 10 Number:

ified. as: wiunotiom oi ttigi radiation. tmnsmission characteristics oi. said;speo1men-.-

REFERENCES? cm The following references- 511E of? recoxdi ml the me of this patent:

UNITED STATES PATENTS Name: Data 

